The present invention relates to a pinion clutch for a starter, and, more particularly, to a pinion clutch capable of improving reliability in pinion meshing and of reducing impact torque which can be generated upon meshing
As disclosed in Japanese Patent Examined Publication No. 54-30061, conventional pinion clutches for starters are arranged such that a spline tube is disposed on a drive shaft, with the spline tube having a first helical spline on the inner surface thereof and a second helical spline on the outer surface of the same. Thus, the inner surface of the spline tube is engaged to the drive shaft through the first helical spline, while the outer surface of the spline tube is engaged to a clutch-outer through the second helical spline. Furthermore, rollers are disposed between a clutch-inner and the clutch-outer, the clutch-inner being integrally formed with the pinion. Thus, a pinion clutch having a one-way clutch function is achieved. In addition, a meshing spring capable of being elastically deformed in the axial direction, when the pinion strikes the ring gear of an engine, is disposed between a sleeve and the clutch-outer, with the sleeve being capable of moving the pinion clutch in the axial direction. Another spring is so disposed between the spline tube and the drive shaft as to be capable of being elastically deformed in the axial direction. As a result, impact torque can be absorbed when the pinion meshes with the ring gear of the engine.
In the conventional pinion clutch of the type described above, the second helical spline on the outer surface of the spline tube is adapted to be meshed with the pinion. The function of the helical spline of this type is the same as that of a conventional pinion clutch which is previous to the above-described conventional clutch, the helical spline of the previous conventional pinion clutch being of the type capable of causing the clutchouter to be engaged to the drive shaft through a single helical spline. That is, the torsional direction of the helical spline is arranged to be in the direction opposite to the rotation of the drive shaft. Therefore, when the sleeve is moved, the pinion is, by the action of the helical spline, caused to move forward and rotated in the direction opposite to the rotation of the drive shaft to be brought into contact and meshed with the ring gear thereafter. The pinion in mesh with the ring gear is caused to further move forward by the action of the helical spline due to the torque of the motor which rotates the drive shaft.
On the other hand, the first helical spline formed on the inner surface of the spline tube is provided for the purpose of absorbing impact torque which can be generated when the pinion meshes with the ring gear, the helical spline being arranged to be twisted in the same direction as that of the rotation of the drive shaft. Therefore, a clip is used to secure the end portion of the spline tube in order to prevent the spline tube from moving toward the ring gear, such clip being located at the end portion of the spline in the direction in which the spline tube moves. As a result, when the pinion meshes with the ring gear and impact torque is thereby generated, the pinion strikes the pinion stopper and the spline tube is retracted in the direction opposite to the ring gear by the action of the helical spline. This leads to the fact that the above-described spring for absorbing the impact torque is so deflexed as to absorb the impact torque.
In the conventional pinion clutch, the two helical splines respectively formed on the inner and outer surfaces of the spline tube do not act in cooperation with each other when the pinion meshes with the ring gear. The helical spline formed on the outer surface acts solely. Similar to the single helical spline of the previous conventional pinion clutch, the conventional helical spline simply causes the pinion to move forward after the pinion has meshed with the ring gear, that is, the helical spline performs a meshing action. The conventional helical spline cannot eliminate the possibility of failure in establishing the meshing when the pinion strikes the ring gear. Therefore, reliability in the meshing cannot be improved. In other words, the above-described conventional pinion clutch has been arranged such that the performance of absorbing impact torque and reliability in pinion meshing are improved by individual means. No pinion clutch in which the performance of absorbing impact torque and the reliability in pinion meshing are simultaneously improved has yet been realized.